ARTICLE Courtship tactics by male Ilyoplax pusilla (Brachyura, Dotillidae) Asami Kasatani • Keiji Wada • Yoichi Yusa • John H. Christy Received: 27 May 2011 / Accepted: 26 July 2011 / Published online: 21 August 2011 Ó Japan Ethological Society and Springer 2011 Abstract Mating in the dotillid crab Ilyoplax pusilla occurs after the female enters the male’s burrow in the tidal flat. Males use two tactics to cause females to enter their burrows for mating: the male either directs claw waving to the female (courting-wave display), to which the females responds by following the male to his burrow, or the male runs rapidly away from, then back toward, his burrow (dash-out-back display), which startles the female into his burrow. Males more often used the courting-wave than the dash-out-back display, but mating success did not differ between the two tactics. Male use of either tactic was influenced by date, female density and male size; the courting-wave display was used by larger males, later in the breeding period, and under higher female density. Keywords Courtship tactics Á Ocypodoid crab Á Mating success Á Sensory trap signal Á Courtship display Introduction Courting males sometimes use signals that include stimuli to which females respond in other contexts (Christy 1995). Not surprisingly, food is often the model for such mimetic signals: females approach males that use food-like signals as they would approach food (e.g., Proctor 1992; Rodd et al. 2002) and this increases the chance that the male will mate with the female. However, male crabs of some ocy- podoid species sometimes use displays that elicit responses from females that function for escape from predators not for finding food (Christy 2007; Christy and Rittschof 2011). These displays are used by males of at least three fiddler crab species, Uca pugilator, U. terpsichores and U. beebei (Christy and Rittschof 2011) and three species of the dotillid genus Ilyoplax, namely I. pusilla (Wada 1981), I. pingi and I. dentimerosa (Wada et al. 1996). If the bur- row has a courtship structure, such as a sand hood as built by U. terpsichores, the male may move slowly behind the structure, then rapidly over the top, producing the back- and-over display. If the burrow lacks a structure at the entrance, which is always the case for Ilyoplax spp., the male may move quickly away from, then, with its claws raised high, back to, the burrow, producing the dash-out- back display. The female sees the rapidly moving and elevated claws or the body of the displaying male above her visual horizon; stimuli such as these from predators elicit an escape response (Layne 1998), and startle the female to enter the male’s burrow. Although these star- tling displays have been seen frequently, they are less common than the courting-wave display that males usually use to attract females to their burrow. The con- texts that favor the use of these displays are not known. In addition, relative success of these startling displays compared to the more common courting-wave display has not been measured. Here, we report the results of a study of the contexts in which males of the dotillid crab I. pusilla uses the courting- wave and the dash-out-back displays and the relative success of each. A. Kasatani Á K. Wada (&) Á Y. Yusa Department of Biological Science, Faculty of Science, Nara Women’s University, Nara 630-8506, Japan e-mail: mbanzai@cc.nara-wu.ac.jp J. H. Christy Smithsonian Tropical Research Institute, Balboa, Republic of Panama 123 J Ethol (2012) 30:69–74 DOI 10.1007/s10164-011-0296-7